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Drug Interactions between fostemsavir and nafcillin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Minor

nafcillin fostemsavir

Applies to: nafcillin and fostemsavir

Coadministration of fostemsavir with moderate or weak CYP450 3A4 inducers may decrease the plasma concentrations of temsavir, the active moiety of fostemsavir. According to the prescribing information, temsavir is a substrate of CYP450 3A4, esterases, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP). When fostemsavir (600 mg twice daily) was coadministered with the moderate CYP450 3A4 inducer etravirine (200 mg twice daily) in 14 study subjects, mean temsavir peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Ctau) decreased by 48%, 50% and 52%, respectively, compared to fostemsavir administered alone. When the same dosage of fostemsavir was given to 22 study subjects with another moderate CYP450 3A4 inducer, rifabutin (300 mg once daily), mean temsavir Cmax, AUC and Ctau decreased by 27%, 30% and 41%, respectively. These changes are not considered clinically relevant, and no dosage adjustment of fostemsavir is recommended when coadministered with moderate or weak CYP450 3A4 inducers.

References (3)
  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. Cerner Multum, Inc. "Australian Product Information."
  3. (2020) "Product Information. Rukobia (fostemsavir)." ViiV Healthcare

Drug and food interactions

Moderate

nafcillin food

Applies to: nafcillin

ADJUST DOSING INTERVAL: Certain penicillins may exhibit reduced gastrointestinal absorption in the presence of food. The therapeutic effect of the antimicrobial may be reduced.

MANAGEMENT: The interacting penicillin should be administered one hour before or two hours after meals. Penicillin V and amoxicillin are not affected by food and may be given without regard to meals.

References (6)
  1. Neu HC (1974) "Antimicrobial activity and human pharmacology of amoxicillin." J Infect Dis, 129, s123-31
  2. Welling PG, Huang H, Koch PA, Madsen PO (1977) "Bioavailability of ampicillin and amoxicillin in fasted and nonfasted subjects." J Pharm Sci, 66, p. 549-52
  3. McCarthy CG, Finland M (1960) "Absorption and excretion of four penicillins." N Engl J Med, 263, p. 315-26
  4. Cronk GA, Wheatley WB, Fellers GF, Albright H (1960) "The relationship of food intake to the absorption of potassium alpha-phenoxyethyl penicillin and potassium phenoxymethyl penicillin from the gastrointestinal tract." Am J Med Sci, 240, p. 219-25
  5. Klein JO, Sabath LD, Finland M (1963) "Laboratory studies on oxacillin. I: in vitro activity against staphylococci and some other bacterial pathogens. II: absorption and urinary excretion in normal young." Am J Med Sci, 245, p. 399-411
  6. Neuvonen PJ, Elonen E, Pentikainen PJ (1977) "Comparative effect of food on absorption of ampicillin and pivampicillin." J Int Med Res, 5, p. 71-6

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

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